Dwyer HFT - Manual (Page 2)

Selecting the Output
The user may choose between reading a 0-2000 Hz
square wave pulse, a 0-5 VDC analog signal, or a two-
wire 4-20 mA analog signal by connecting to the
appropriate pins on the 4-pin DIN connector and by
placing the programmable jumper in the appropriate
position for the desired output. An analog 1-5 VDC
output may also be obtained by configuring the unit for
the two-wire 4-20 mA output and then placing a 249 Ω
resistor in parallel with the receiver. The exact output
pins and jumper positions that correspond to each
output are discussed later in this manual.
Wiring
4-20 mA output connections:
Input Voltage: The supply voltage must be between 12
and 35 VDC. The maximum resistance that may be
placed within the current loop is given by the following
formula:
R
max
= 50(V
s
- 12)
Where:
R
max
= the maximum resistance that
may be placed in the current loop (Ω).
V
s
= the value of the supply voltage (VDC)
Note: Although the signal conditioning circuit does have
integral over-current protection, it is recommended that
the circuit be protected with a 0.25 amp fuse.
Wiring Instructions:
(Refer to Illustrations 2 & 3)
1) Move the programmable jumper on the signal
conditioning board into the position closest to the
meter’s outlet, as shown in Illustration 3.
2) Connect the positive DC power source (+12 to +35
VDC) to terminal #1 on the DIN connector.
3) Connect terminal #2 of the DIN connector to the
positive current input on the receiving device.
4) If the power source does not originate from the
receiving device, the negative side of the power
supply must be connected to the signal ground of the
receiving device.
5) If the transmitter is operating properly, the green
LED on the signal conditioning board will illuminate
dimly at zero flow and will increase in intensity as
flow increases.
0-5 VDC output connections:
Wiring Instructions:
(Refer to Illustrations 4 & 5)
1) Move the programmable jumper on the circuit board
into the position closest to the meter’s inlet, as
shown in Illustration 5.
2) Connect the positive voltage source (+12 to +35
VDC) to terminal #1 of the DIN connector.
3) Connect terminal #2 of the DIN connector to the
negative side of the DC voltage source.
4) Connect terminal #3 of the DIN connector to the 0-5
VDC input of the receiving device.
5) If the power source does not originate at the
receiving device, a wire will need to be connected
between the negative side of the voltage source and
the signal ground of the receiving device.
6) If the transmitter is operating correctly, the green
LED on the circuit board will illuminate brightly when
power is applied to the unit.
Note: The input impedance (resistance) of the receiving
device must not be lower than 100 Ω or non-linearities
may result. Lower impedance will not damage the
transmitter.
NO CONNECTION
G
2
3
1
PIN #1
+12-35 VDC
PIN #2
4-20 mA OUT
ELECTRICAL CONNECTIONS - 4-20 mA
Illustration 2
NO CONNECTION
PROGRAMMABLE JUMPER
IN POSITION CLOSEST
TO METER OUTLET
JUMPER POSITION - 4-20 mA
Illustration 3